Patent GB-146425-A (GB)
Title: Telephone exchange systems
IPC: H04Q3/42
Filed: 1920-07-03
Abstract: 146,425. Western Electric Co., (Assignees of Lundell, A. E.). Dec. 29, 1916, [Convention date]. Automatic and semi-automatic exchange systems.-A sending-equipment (for example, a set of registers and a device for counting reverting impulses) and a setting-equipment (for example, an operator's keyboard) are temporarily associated for the establishment of each call. Thus, in a semi-automatic system, there may be a single keyboard for each operator and a group of sending- equipments common to the operators. In the system illustrated, when a cord 105, Fig. 1, is taken into ues by an operator, an associated sequence switch 202, Fig. 2, connects the operator's keyboard, Figs. 3 and 4, to terminals individual to the cord in the banks of a group of cord-finders. One of these finding-switches, Fig. 5, connects itself to the cord, and an associated sender-selector hunts for an idle sending-equipment, consisting of a counting-switch, Fig. 6, and a set of registers, Figs. 7 and 8. The wanted number is written on the keyboard, which impresses it on the registers, and the keyboard is then at once released for use on other calls. Each register consists of one sensitive and two marginal relays, which are controlled from the keyboard by two currents, either weak or strong, so that a particular combination of relays is energized and closes a corresponding marking-circuit. Since the selectors are 500-point switches, the record impressed on the registers is a non-decimal translation of the number written on the keyboard. The connexion is completed by a district selector, Fig. 1, and office selector, Fig. 9, at the calling exchange and by an incoming selector, Fig. 10, and final selector, Fig. 11, at a second exchange. Each of these selectors is a powerdriven switch with 500 sets of terminals arranged in a vertical row and divided into 5 sections served by different sets of brushes. The 100 sets of terminals served by each set of brushes are divided into 10 groups of 10 or (in the case of the incoming selector) into 4 groups of 25. The shaft which carries the five sets of brushes is lifted in three successive stages ; the first movement brings one of the sets of brushes into tripping-position; the second movement (a tripping-magnet being now energized) trips the selected brushes so that they can engage the terminal bank and carries them to one of the groups of 10 or 25 terminals; the third movement positions the tripped brushes on a particular set of terminals (or on the first idle set) of the selected-group. In the case of the first or district selector the first of these movements is omitted, the tripping of the proper set of brushes being determined by a series of magnets one of which is energized directly from the keyboard. In the course of each numericallyselective movement, a commutator such as 133, Fig. 1, sends back reverting impulses in known manner over a fundamental circuit to rotate the counting-switch shown at the left of Fig. 6, and when this switch reaches the marking-circuit closed by the register which controls the movement in question it opens the fundamental circuit and brings the movement to a stop. As soon as the wanted line has been selected, the sending- equipment is released for other service. Operation of cord-finder and sender-selector, Fig. 5. The cord-finders are switches of the same general type as the numerical selectors, having 500 sets of terminals divided into 5 sections served by different sets of brushes. The groups of cords belonging to different operators are connected to different sections of the terminal banks, a magnet of the series 541, 541<A>, &c. being energized to trip the set of brushes serving the section in which a call arrives. A single set of trip magnets is provided for the whole group of finders (the magnet 541 for example puts a trip in the path of the first set of brushes in each finder), this being possible because the finders can only be taken into use one at a time, under the control of an allotting-switch 583. When an operator plugs a cord 105 into a calling jack, sleeve relay 103 moves switch 202 to its 7th position, bringing the operator's speaking-set 200 into action and connecting the keyboard to circuits 566, 227, 225 leading to terminals individual to the cord in the cord-finder banks. Contact 208 energizes relay 211, which locks itself up, and contact 206 moves the switch 108 to its 2nd position. A circuit 585 is now closed to energize relay 501, which locks itself in series with relays 511, 514 to the wire 111, which has been grounded by the contact 112, and a branch of the same circuit energizes a trip magnet 541 which moves a trip 542 in each finder of the group into the path of the set of brushes serving the group of cords to which the cord 105 belongs. The finder preselected by the alloting switch 583, which alone has its sequence switch 516 in its 1st position ready for service, is now started by the energization of.relay 514, which energizes relays 517, 522 to move the switch 516 to its 2nd position. The lifting-magnet 525 is energized under control of relay 522, which is now energized over a back contact of relay 545, and lifting-magnet 529 is energized under control of relay 517, which has locked itself to the test-brush 520. The cordfinder rices through its tripping position, in which the selected set of brushes is tripped, and these brushes are then carried over the terminal bank, but before they reach the first set of terminals a circuit is closed through contact 573 to energize relay 500, which locks itself and de-energizes relays 501, 511, 514 and tripping-magnet 541. The de-energization of relay 514 moves the switch 516 to its 3rd position. When the finder reaches the calling cord, relay 545 is energized over both its windings in series and short-circuits its high-resistance winding, and as soon as the brush 536 reaches the next insulating segment of the commutator 549, i.e. when the brushes are properly centred on the terminals, relay 522 relapses, opencircuiting magnet 525 and moving switch 516 to its 4th position. In the meantime the sender selector has been searching for an idle sender, and as soon as the brush 520 is centred on an ungrounded test terminal relay 517 relapses, opencircuiting magnet 529 and moving switch 516 from its 4th to its 15th position. Preventing double connexions by cord-finders. If two cords belonging to different operators, and therefore served by different sets of brushes in the cord-finders, are simultaneously taken into use, two trip-magnets such as 541, 541<A> may be energized at the same time, so that two sets of brushes would be tripped and the finder would make a double connexion. This is prevented by the arrangement shown in the bottom right-hand corner of Fig 5, comprising a switch 509 common to the group of finders, in conjunction with the circuits shown in the bottom left-hand corner of the same figure, which are common to the group of cords belonging to an operator. Each pair of ter. minals of the switch 509 is individual to a group of cords. In the case imagined, there would be ground connexions on two wires 111 and a marginal relay 503 receives sufficient current through resistances 502 to become energized, closing the circuit of the stepping-magnet 505 of switch 509. When the wiper 508 reaches the terminal of a group of cords which includes one of the calling cords, the switch is arrested by the energization of relay 504, which energizes relay 512, which locks itself over wiper 507 in series with relays 501, 511, 514. Relay 501 energizes the tripping- magnet 541, short-circuits relay 512, locks itself to the wire 111, and disconnects this wire from relays 503, 504. Relay 503 remains energized over the wire 111 of the other calling cord, but relav 504 relapses. Relay 514 energizes relays 517, 522 to start the finder, as already described, and the relapse of relay 504 starts the switch 509 again to find the group of cords containing the other calling cord. As soon as the first finder has passed its tripping position and energized relay 500, the de-energization of relays 501, 511, 514 allows relay 512 to become energized again, with the result that a second trip magnet such as 541A is energized to trip the appropriate set of brushes in a second finder, which is now set in action by the allotting-switch 583. Operation of the finder allotting-switch 583, Fig. 5. As soon as the cord-finder and senderselector have set themselves, a circuit 580 is closed through the switch 583, which moves forward to select the next idle finder having its sequence switch 516 in the 18th or waiting position, and a circuit such as 586, 567 is closed to move the sequence switch of this finder to its 1st position. Preventing connexion of an operator's keyboard to two cord-circuits simultaneously. If the operator, after writing down the wanted number on her keyboard, takes a second cord into use to answer another call, the switch 202 of the second cord moves to its 7th position and the keyboard is connected simultaneously to both cords. In a modification of the circuits shown in Fig. 2, and described in the Specification as open to inspection under Sect. 91 (3) (a), this is prevented by giving the switches 202 two listening positions, the keyboard circuits being completed only in the second of these positions. A switch 202 moves automatically through the first of these positions to the second unless another switch is already standing in the second position, in which case it is arrested in the first position until the keyboard is clear of the first call. Thus the operator can speak with the second caller without risk of false keyboard connexions. This subject-matter does not appear in the Specification as accepted. Setting of the sending registers, Figs. 7 and 8, by the operator's keyboard, Figs. 3 and 4. The keyboard comprises so-called tandem hund